Locomotive wheel inspection with EMAT technology

There is a need to analyze locomotive wheels for flank cracks in a non-destructive manner in order to prevent catastrophic failures. Flaw, shape, and size are desired parameters in establishing the quality of commercial tires. A variety of defects such as voids, inclusions, surface and internal cracks, or the like, must be discerned in order to prevent failure. This paper exhibits and compares the benefits of a number of different techniques used for flaw detection. Non-destructive evaluation (NDE) techniques used are magnetic particle inspection, dye penetrant, eddy current, electro-magnetic acoustic transducer (EMAT). The techniques vary in their ability to ascertain the flaw characteristics. Using a non-contact sensor such as the EMAT, to scan the wheels in an automated manner offers greater inspection speed at lower manpower. This paper reviews the basic concept of EMATs, introduces a recently developed technique for simulating EMAT performance by Finite Element calculation and features bench top results of waveform acquisition and signal-to-noise ratio dependence on lift-off. Next presented are calibration results for spark-eroded flaws in wheel sections for a variety of locations and sizes. Finally data are on flaw detection in a railroad service facility on several locomotives with wheels spinning at speeds up to 40 meters/minute. Results for both artificial and actual flaws are shown.